1. Field of the Disclosure
The present invention relates to carpets and methods for making and recycling carpets. More specifically, the carpet may be tufted and possess one or more backing layers.
2. Description of the Prior Art
Tufted carpets are composite structures in which the face fiber forming the pile, i.e., the surface of the carpet, is needled through a primary backing and the base of each tuft extends through the primary backing and is exposed on the bottom surface of the primary backing.
The basic manufacturing approach to the commercial production of tufted carpeting is to start with a woven scrim or primary carpet backing and to feed this into a tufting machine or a loom. The carpet face fiber is needled through and embedded in the primary carpet backing thus forming a tufted base or griege goods. Griege goods are typically backed with an adhesive coating in order to secure the face fiber to the primary backing. Low cost carpet often receives only a latex adhesive coating as the backing. This type of carpet is widely used in boats and is called marine backed carpet. Typically, the marine backed carpets are backed with a latex adhesive coating that is water and/or mildew resistant. Higher cost carpet often receives both a secondary backing and a latex adhesive coating.
The face fiber or yarn used in forming the pile of a tufted carpet is typically made of any one of a number of types of fiber, e.g., nylon, acrylics, polypropylene, polyethylene, polyamides, polyesters, wool, cotton, rayon and the like.
Primary backings for tufted pile carpets are typically woven or non-woven fabrics made of one or more natural or synthetic fibers or yarns, such as jute, wool, polypropylene, polyethylene, polyamides, polyesters, and rayon. Films of synthetic materials, such as polypropylene, polyethylene and ethylene-propylene copolymers may also be used to form the primary backing.
Likewise, secondary backings for tufted pile carpets are typically woven or non-woven fabrics made of one or more natural or synthetic fibers or yarns. Preferably, secondary backings for tufted pile carpets are open weave or leno weave, i.e., tape yarn in the warp direction and spun staple fiber in the fill direction. The spun staple fiber is more costly but desirable to increase adhesion between the backing and the latex adhesive.
The application of the latex adhesive coating involves preparing griege goods by stitching a primary carpet backing material with face fiber in a manner so as to form on the top surface of the material a pile composed of numerous closely spaced, up-standing loops of yarn. Thereafter, the bottom surface of the thus formed griege goods is coated with a latex polymer binder such as a styrene-butadiene copolymer. The coated griege goods are then passed through an oven to dry the latex adhesive coating to bond the face fibers to the primary backing which causes the bonding of and which is the principal reason for adding the latex binder.
If desired, a secondary backing may be bonded to the undersurface of the primary backing. To produce tufted carpets with a secondary backing, the bottom surface of the griege goods is coated with a latex polymer binder. Then, the secondary backing is applied to the coated bottom surface and the resulting structure is passed through an oven to dry the latex adhesive coating to bond the secondary backing to the griege goods.
The above-described method for making carpet is used in 80 to 90% of all carpet made in the United States. This carpet-making method has disadvantages in that it requires a drying step and thus an oven to dry the latex polymer binder. The drying step increases the cost of the carpet and limits production speed. Furthermore, it has recently been reported that latex adhesive compositions generate gases that may be the cause of headaches, watery eyes, breathing difficulties and nausea, especially when used in tightly sealed buildings. See Herligy, The Carpet & Rug Industry. October 1990. In addition, overheating of the carpet may occur during drying of the latex which in turn may affect the shade of the carpet.
Consequently, carpet manufacturers have been attempting to develop a new approach for the preparation of tufted carpets. One new approach is the preparation of tufted carpets with a hot-melt adhesive composition instead of a latex composition.
Hot-melt adhesives are amorphous polymers that soften and flow sufficiently to wet and penetrate the backing surfaces and tuft stitches of carpets upon application of sufficient heat. Furthermore, hot-melt adhesives tend to adhere to the backing surfaces and/or tuft stitches. That is, hot-melt adhesives stick to backing surfaces and tuft stitches.
By the use of hot-melt adhesive, the necessity of drying the composition after application is eliminated and further, when a secondary backing material is desired, it can be applied directly after the hot-melt composition is applied with no necessity for a drying step.
Application of a hot-melt composition is generally accomplished by passing the bottom surface of the griege goods over an applicator roll positioned in a reservoir containing the hot-melt composition in a molten state. A doctor blade is ordinarily employed to control the amount of adhesive which is transferred from the application roll to the bottom surface of the structure. After application of the hot-melt composition to the bottom surface of the griege goods, and prior to cooling, the secondary backing, if desired, is brought into contact with the bottom surface, and the resulting structure is then passed through nip rolls and heated.
The activation temperature of a hot-melt adhesive, i.e., the temperature at which the adhesive softens and flows sufficiently to wet and penetrate the backing surfaces and tuft stitches, is below the temperature at which the backing and face yarns melt or otherwise distort. Otherwise, the backing and face yarns may suffer other damage due to heating.
Hot-melt adhesives also must have low enough viscosities at temperatures employed in finishing to achieve good wetting of the backings and sufficient encapsulation of tuft stitches to make the tuft yarns resistant to pull-out, pilling and fuzzing. In addition, for commercial practice, economics of a carpet manufacturing process utilizing hot-melt adhesive must be at least as good as those of conventional latex lamination techniques which remain the dominant lamination process in commercial carpet manufacture.
A number of hot-melt adhesives and processes using the hot-melt adhesive have been proposed for use in carpet lamination. For example, U.S. Pat. No. 3,551,231, issued Dec. 29, 1970 to Smedberg, discloses a hot-melt adhesive carpet lamination process in which molten adhesive consisting of an ethylene-vinyl acetate copolymer and, optionally, waxes (e.g., microcrystalline and polyethylene waxes), fillers (e.g., calcium carbonate), resin extenders (e.g., dicyclopentadiene alkylation polymers) and antioxidant is applied to a tufted primary backing and then a secondary backing is contacted with the molten adhesive under pressure after which the assembly is cooled to solidify the adhesive.
U.S. Pat. No. 3,583,936, issued Jun. 8, 1971 to Stahl, discloses a hot-melt adhesive for tufted carpet lamination comprising about 10-35 weight percent ethylene copolymer comprising about 60-85 weight percent ethylene, and about 15-40 weight percent lower vinyl ester, acrylate or methacrylate; about 10-25 weight percent wax, such as microcrystalline petroleum, polyolefin, or paraffin wax having a melting point sufficient to give an adhesive composition with a softening point greater than 190.degree. F.; and about 50-70 weight percent resin extender composed of a base resin prepared from reactive olefins and diene monomers of 5-7 carbons.
The hot-melt compositions are selected for their adhesive properties. That is, the hot-melt composition may be selected for their suitability in adhering the tufts of face yarn to the primary backing and to adhere the secondary backing to the primary backing. Such compositions are generally amorphous or substantially non-crystalline due to the adhesive properties of such polymers.
For example, U.S. Pat. No. 3,982,051, issued Sep. 21, 1976 to Taft et al., discloses a carpet containing a hot-melt composition of ethylene copolymer, atactic polypropylene and vulcanized rubber. The atactic, substantially non-crystalline, polypropylene used in the hot-melt composition may be obtained as a by-product from the preparation of substantially crystalline, isotactic, polypropylene. Atactic polypropylene is particularly suitable as a hot-melt composition due to its adhesive nature whereas isotactic polypropylene is not particularly suitable as a hot-melt composition due to its lack of adhesive properties.
Other patents that disclose various hot-melt compositions used in the manufacture of carpet include U.S. Pat. Nos. 4,875,954; 4,844,765; 4,576,665; 4,522,857; Re. 31,826; 3,940,525; B 501,415; 3,676,280; 3,537,946; 3,390,035; and British patent publication 971,958.
While the hot-melt compositions and processes heretofore known are considerably simpler than the latex process, the preparation of carpets of non-uniform quality has, at times, been encountered. Specifically, such carpets using hot-melt adhesives cannot, with reproducible consistency, be prepared with high scrim bonds (force required to remove the secondary backing from the finished carpet), high tuft pull strength (force required to pull one of the tufts out of the carpet), and high fuzz resistance (an indication of the individual carpet yarns to fuzz and form pills). Thus, while such hot-melt compositions are appealing from a standpoint of cost, speed and safety, some difficulties have been encountered in preparing completely satisfactory carpet. See U.S. Pat. No. 3,551,231, issued Dec. 29, 1970 to Smedberg.
Furthermore, neither the latex adhesive based carpet nor the hot-melt adhesive based carpet may be recycled. Thus, large quantities of carpet trimmings and scrap produced during the manufacture of carpet and used carpet are sent to landfills. Consequently, carpet manufacturers spend a substantial sum on landfill costs.
Thus, while conventional carpet and carpet manufacturing processes are known, these carpets and manufacturing processes have inherent problems due to the compositions employed therein. Specifically, the adhesives used to adhere the tufts of face fiber to the primary backing and to adhere the secondary backing to the primary backing include compositions which require lengthy drying times thus slowing down the manufacturing process. In addition, the latex compositions may produce noxious off gases which create health hazards. Likewise, many of the hot-melt compositions conventionally employed in the manufacture of carpet do not result in reproducible consistency regarding scrim bonds, tuft pull strength and fuzz resistance. Finally, and most importantly, the use of conventional latex adhesives and hot-melt adhesives prevent carpet from being recycled.
From the above background, it is quite apparent that there is need in the art for an improved carpet and method for producing carpet as well as a method for recycling carpet.